Genetic variability suggests that three populations of Ceratocystis fimbriata are responsible for the Ceratocystis wilt epidemic on kiwifruit in Brazil
Ceratocystis fimbriata is a native, soilborne pathogen in South America that causes a lethal wilt disease on a broad range of economically important plants. Ceratocystis wilt on kiwifruit (Actinidia spp.) was first recognized in 2010 in the state of Rio Grande do Sul, Brazil. The genetic variation among kiwifruit isolates was analized to determine if a single introduced strain of the pathogen was responsible for the epidemic or if there was substantial genetic variation in the population, suggesting that the fungus was soilborne and indigenous to the region. We used 14 microsatellite (simple sequence repeat, SSR) markers to identify 18 genotypes of C. fimbriata among 76 isolates from eight kiwifruit farms. The 18 genotypes clustered into three groups based on UPGMA analysis of the microsatellite alleles. The largest group comprised 60 isolates of 11 closely-related microsatellite genotypes obtained from seven of the eight farms. These genotypes appeared to have originated from a single farm that had supplied cuttings for grafting to the other farms. The population of the pathogen from the farm that supplied the cuttings had the highest level of genotypic diversity and relatively high gene diversity, suggesting that this source population represented an indigenous, soilborne population. Phylogenetic analyses of the DNA sequences of the mating type locus (including portions of MAT1-1-2 and MAT1-2-1) placed the isolates into three groups, corresponding to the three microsatellite groups. Most of the isolates, including all the tested isolates from the farm that supplied the cuttings, had mating type gene sequences that were distinct from other Brazilian populations of C. fimbriata. A second group comprised isolates from one farm that had mating type gene sequences typical of Mata Atlântica (Rio de Janeiro and São Paulo) populations of C. fimbriata on Colocasia esculenta and Mangifera indica. Three farms purchased kiwifruit plants or rootstocks from commercial nurseries in Brazil as well as scions from the source farm, and some of the isolates from these farms were genetically similar to Eucalyptus isolates of C. fimbriata from Bahia and Minas Gerais, Brazil. The kiwifruit epidemic in Rio Grande do Sul is the southern-most report of C. fimbriata in Brazil, and the primary pathogen population on kiwifruit appears to be indigenous and originated from a single farm that distributed the pathogen in grafting material. In addition, commercial nursery stock was also implicated as sources of C. fimbriata genotypes. The disease is a major limiting factor for kiwifruit production in southern Brazil, and the results suggest that clean planting stock will be important to successful production.
KeywordsActinidia spp Genetic diversity Kiwifruit disease Latin American Clade Microsatellite Phylogeny
This research was supported by Vale, CNPq, FAPEMIG and CAPES. We thank the growers, Dr. Lucas Garrido and Dr. Samar Velho da Silveira (Embrapa Uva e Vinho), and Alfredo Galina (Emater) for providing invaluable assistance in collection of isolates and in reconstructing the history of kiwifruit cultivation in the area.
- CAB International (2001) Ceratocystis fimbriata (original text prepared by T.C. Harrington and C. Baker). In: Crop Protection Compendium. CAB International, WallingfordGoogle Scholar
- Castellani A (1939) Viability of some pathogenic fungi in distilled water. Am J Trop Med Hyg 24:270–276Google Scholar
- Ferreira MA, Harrington TC, Gongora-Canul CC, Mafia RG, Zauza EAV, Alfenas AC (2013) Spatial-temporal patterns of Ceratocystis wilt in Eucalyptus plantations in Brazil. For Pathol 43:153–164Google Scholar
- Grellmann EO (2005) Cultura do quivizeiro. SENAR-RS, Porto AlegreGoogle Scholar
- Harrington TC (2013) Ceratocystis diseases. Pp. 230–255 In: Infectious Forest Diseases. Gonthier P and Nicolotti G, eds. CAB International, WallingfordGoogle Scholar
- Moller WJ, DeVay JE (1968) Carrot as a species-selective isolation medium for Ceratocystis fimbriata. Phytopathology 58:123–124Google Scholar
- Oliveira LSS, Harington TC, Ferreira MA, Damacena MB, Al-Sadi AM, Al-Mahmooli HIS, Alfenas AC (2015) Species or genotypes? Reassessment of four recently described species of the Ceratocystis wilt pathogen, Ceratocystis fimbriata, on Mangifera indica. Phytopathology 105:1229–44Google Scholar
- Sônego OR, Ferreira MA, Valdebenito-Sanhueza RM, Gava R, Garrido LDAR, Alfenas AC (2010) Primeiro relato da murcha-de-ceratocystis em kiwi. Trop Plant Pathol 35:233Google Scholar
- Swofford DL (1998) PAUP*. Phylogenetic Analysis Using Parsimony (*and Other Methods), Version 4. Sinauer Associates, SunderlandGoogle Scholar
- Yeh FC, Boyle TJ (1997) Population genetic analysis of co-dominant and dominant markers and quantitative traits. Belg J Bot 129:157Google Scholar